Some early TS-950SD transceivers may exhibit a low Signal to Noise ratio on ten and fifteen meters. In addition, rotating the encoder may allow the user to hear a crackling noise in his headphones. The following modification will correct this condition.

Note: This modification has already been performed on model from serial number 101xxxx.

1. Disconnect the power cord and antenna.
   
    
2. Remove the top and bottom covers (18 screws).
   
    
3. Open the sub chassis as shown in figure 1 (remove 4 top screws, remove 3 back panel screws, unplug the RX ANT OUT and DRIVE IN connectors).
   
    
4. Remove the cover from the sub chassis (12 screws). Figure 1.
   
    
5. Remove the 9 screws from the Filter board.
   
    
6. Desolder the antenna connector wires at the antenna connector. Do not damage the surge absorber.
   
    
7. Rotate the Filter unit to expose the foil side of the board. Disconnect coax cables as necessary to rotate the board and remove the mesh plate as the board is rotated.
   
    
8. Cut the two foils as shown in figure 2.
   
    
9. Assemble the transceiver by reversing steps 1 - 7. Remember to install the mesh plate, resolder the antenna connector, and plug in the two connectors on the back panel.

This modification is covered under the 1 year warranty.
Time required to perform the modification is 1 hour or less.

It is possible to exceed the maximum Vcbo rating of the MRF429 transistors used in the TS-950S/SD if the unit is operated at excessive transmit power levels (greater then the normal factory output power setting). This results in a collector to base short on the MRF429. This causes excessive current to be drawn thru R17 and or R18 of the final bias circuit. This can cause a large amount of smoke from the overloaded resistors. It does not normally cause damage to surrounding components. (You might wish to check Q7, VR2, Q8 and the fuse just as a precaution!)

R17 and R18 are carbon type resistors (27 ohms ½ w). Carbon resistors can emit quite a bit of smoke when overload in this manner and can be the cause of considerable concern by the operator!

In order to case operator concern we recommend replacing R17, and R18 on the final unit (X45-3330-00) with ceramic resistors whenever replacing the final transistors. These special resistors have been designed to open quickly if the current rating is exceeded. This prevents smoking and the odors associated with burning resistors.

Parts required:
27 ohm ½ watt ceramic resistor, (R92-1286-05)

Precautions:

1. The MRF-429 transistors generally fail one of two ways:
   
    
   1. The collector/base junction opens. R17 and R18 are not damage when this occurs.
      
       
   2. If the MRF-429's are operated at RF power levels higher then the absolute maximum Vcbo rating the collector/base junction fails. This causes excessive current to flow thru the base circuit.

   
   
    

2. If the MRF-429's short collector to base with ceramic resistors there will be very little smoke before the resistor opens. The outward appearance of the resistors will not change, so you must make sure to check the resistors with an ohmmeter before installing new finals.
   
    
3. If R17 or R18 should open there will not be an appreciable change in the base circuit current. It is essential, however, that these resistors be in good working order as they ensure stable operation of the final amplifiers.
   
    
4. R17 and R18 must be replaced whenever you replace the final transistors. The ceramic resistors are easy to identify. They are rectangular and white in color.

Replacement Procedure:

1. Replace the bad MRF-429 transistors.
   
    
2. Remove R17 and R18 from the component side of the Final circuit board.
   
    
3. Solder the ceramic resistor directly to the base and emitter of the final transistors. The stability of the circuit is improved by soldering R17 and R18 directly to the base and emitter of the finals. Do not install them in the old locations!

The 50 watt power down circuit will begin to operate if the cooling fan on the rear panel fails to operate after 15 minutes of continuous transmission in order to protect the final amplifier circuit. Failure of the fan will prevent the power down circuit from returning transmit power to normal levels since the transformer temperature remains high. This trouble can sometimes be traced to a pinched/burnt wire near resistor R17 of the AVR unit (X43-3070-01).

Causes:

If the red wire attached to the connector CN2 of the AVR unit is pinched between the chassis and ground the insulation might be damage and allow this line to be short to the chassis. This wire supplies 15 Vdc to the fan motor thru resistor R17. Excessive current is drawn thru R17 under this circumstance, approximately 1.5 A rather then the normal .5 A. This can cause the resistor to become red hot and damage the surrounding circuit board, since R17 is a metal oxide film resistor.

Corrective action:

R17 should be replaced with a ceramic resistor if this symptom is encountered. Replacing the metal oxide film resistor with a ceramic resistor will prevent damage to the circuit board should the red lead become shorted.

Parts required:
10 ohm 2 watt ceramic resistor, R92-1285-05

Occasionally the TS-950SDX will transmit instantaneously when the mode is switched from SSB to CW with the VOX turned on. The frequency of occurrence depends upon the setting of the VOX GAIN and DELAY controls.

Cause:

A small amount of RF feedback is felt on analog switches IC5 and IC6 in the AF unit. This RF causes the timing circuit to actuate briefly when the mode is changed with VOX ON.

Warning: This radio uses micro-sized surface mount component, and/or multi-layer circuit boards. If you are not familiar with the techniques for service of this type of equipment do not attempt this modification yourself. You will invalidate your warranty if you attempt to modify the equipment and damage the radio. If you are at all in doubt about your qualification to perform this modification you should seek qualified assistance.

Required parts:
C191: 4.7 µF, 25 V electrolytic capacitor (CW04EW1W4R7M)

Procedure:

1. Unplug the DSP unit from the rear of the transceiver.
   
    
2. Remove the top and bottom covers (18 screws).
   
    
3. Turn the units so the bottom is up.
   
    
4. The AF unit is located in the front left hand corner.
   
    
5. Remove the 8 screws securing the AF unit to the chassis.
   
    
6. Add C191 in the position indicated in figure 2.
   
    
7. Reverse steps 1 - 5 to reassemble.

This modification may be covered under warranty.
Time required for this modification is 1 hour or less.

We have received several reports of minor distortion of the DRU-2 transmitted audio when used with the TS-950SDX. Recordings made from incoming received sources do not appear to be distorted.

Cause: This characteristic is caused by an impedance mismatch between the DRU-2 output and the input of the microphone amplifier circuit in the TS-950SDX. The following modification will correct/improve this characteristic.

Procedure:
On the Microphone Amplifier Unit (X59-3710-01), which is part of Switch Unit (A) (A41-3240-00) (H/10): (The Microphone Amplifier Unit is a small daughter board located on the switch assembly that has the Microphone Gain/Power Output Control and the Speech Processor IN/OUT controls).

1. Change chip resistor R257 from 4.7 Kohm to 8.2 Kohm (RK73FB2A822J)
   
    
2. Change chip resistor R262 from 4.7 Kohm to 1.5 Kohm (RK73FB2A152J)

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.
 

We have received several reports of the transmitter unkeying when using the K1EA Contesting program. This symptom only occurs when the TS-950SDX is used with version 8 of the K1EA program. Apparently some of the more advanced control features of this new version of the program cause the radio to think the program has unkeying. A new EPROM is available that corrects this transmitter drop out.

Parts required:
IC-19 Microprocessor, (27C512RJDVF), QTY. 1

Procedure:

1. Remove the top and bottom covers of the TS-950SDX.
   
    
2. Carefully unplug the two DSP units cables from the rear of the transceiver.
   
    
3. The front panel of the radio is designed to allow it to be tilted forward for ease of service. To tilt the front panel forward remove the screw at the top of the brackets that secure the front panel to the chassis. (Please refer to the Accompanying diagram). There is one screw on each side of the front panel.
   
    
4. Next loosen the remaining screw at the bottom of each bracket.
   
    
5. Gently pull the bottom of the front panel forward until it reaches the end of the slot in the bracket and gently pull the top of the front panel down.
   
    
6. Now look at the circuit board mounted vertically on the main chassis. This is the Digital Unit (X46-3130-11). Near the center of this board you will find the lithium battery for memory backup and a large IC installed in a socket. This is the EPROM.
   
    
7. Carefully remove the IC from the socket. Use an IC pull or very gently pry it out by slipping a small flat tool between the IC and the socket. Do not use excessive pressure as you can damage the circuit board if you pry too hard!
   
    
8. Take the new EPROM and carefully install it in the now vacant socket. Note that the notch on the end of the EPROM should be down.
   
    
9. Reverse steps 1 - 5 to reassemble. Make certain you do not pinch any wires when you return the front panel to its vertical position.
   
    
10. You will need to reset the microprocessor after the radio is reassembled. This is done by pressing and holding the A=B key while the power is turned on, and then release the key.

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.
 

Symptom:
Reports of low COMP meter sensitivity, or noise on the transmitted audio when using the speech processor is normally a result of misadjustment of the PROC IN control. This control is very sensitive and is difficult to adjust properly.

Parts required:
150 ohm chip resistor, (RK73FB2A151J)

Procedure:
Change the value of R258 in the SIG unit (X57-4130-00) from 68 ohm to 150 ohm. This will increase the available adjustment range of the PROC IN control. This will make it much easier to properly adjust the control and thus avoid overdriving the speech processor circuit.

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.
 

Symptom:
3rd order IMD figures have been noted that do not meet out standard value of -32 to -35 dB.

Cause:
We have found that this symptom can be caused by either improper blas to the final transistor and/or because of distortion inducted by the 73.05 MHz IF mixer circuit.

Parts required:
R195, R197, R198    150 ohm chip resistor   RK73FB2A151J     QTY. 3
R204                4.7 Kohm chip resistor  RK73FB2A472J     QTY. 1
R19, R20            22 ohm carbon resistor  RC05GF2H220J     QTY. 2

Procedure:

1. On the Final unit (X54-3450-00) change R19 and R20 from 10 ohm to 22 ohm. Figure 1.
   
    
2. On the IF unit (X48-3100-00): Figure 2.
   1. Change R195 from 56 ohm to 150 ohm.
   2. Change R197 from 220 ohm to 150 ohm.
   3. Change R198 from 220 ohm to 150 ohm.
   4. Change R204 from 10 Kohm to 4.7 Kohm.

   
   
   No additional adjustment or modification will be required.

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 1 hour or less.
 

Symptom:
A "bug" type Keyer used at high keying speeds might cause a key click or chattering noise on the transmitted signal. When the internal electronic keyer is used no such chattering noise is encountered.

Cause: The internal chatter absorption filter circuit incorrectly tries to remove noise from the external Keyer.

Procedure:

1. Press the MENU key one time.
   
    
2. Select MENU no. 12 by tuning the M.CH knob.
   
    
3. Press the UP key until OFF appears in the display.
   
    
4. Press the MENU key one time to exit the MANU mode.
   
    
5. Turn off the POWER SW.
   
    
6. Turn ON the POWER SW while depressing the MENU key.
   
    
7. Select MENU 69 by tuning the M.CH knob.
   
    
8. Press the DOWN key until OFF appears in the display.
   
    
9. Press the MENU key one time to exit the MENU mode.

This operation turns off the internal chatter absorption filter circuit.

Time required for this modification is 15 minutes or less.
 

Symptom:
On early versions of the TS-950 series (below serial number 106xxx) a hum might be heard when the MONI function is active and headphones are connected to the PHONE jack. No hum is experienced when the MONI circuit is OFF

Cause:
This noise can only be found in the monitor circuit itself and not on the transmitted signal. We have found that the VCO shield cover for the PLL unit might be contacting the shield plate for the filter unit. This physical contact can allow a slight amount of vibration to be felt in the sub-receiver section. This vibration, combined with too much gain in the sub-receiver section contributes to the hum.

Parts required:

Qty    Description                     Kenwood Part No.    Circuit description
 4     Low profile PLL Unit cover screws    N35-2640-05         NA

Procedure:

1. On the IF unit (X48-3060-00) adjust VR-1 to the point the audio output just decreases when the MONI circuit is activated.
   
    
2. Replace the screws on the VCO unit shield case with the new low profile screws.

Time required for this modification is 15 minutes or less.
 

Symptom:
Noise is generated when NB1 is switched on for the sub-receiver.

Cause:
Switching noise from the noise-blanker gate enters the AF amplifier via the +15 V line causing the noise.

Parts required:

Qty   Description                      Kenwood Part No.     Circuit description
 1    100 µF, 16 V electrolytic capacitor  CE04KW1C101M         NA
 1    120 ohm resistor                     RD14BB2B121J         NA

Procedure:

1. Cut the pattern of the 15 V line on the IF unit (X48-3060-00) component side, near Q34's emitter and add the 120 ohm resistor as shown in the accompanying diagram.
   
    
2. Add the electrolytic capacitor as shown in the diagram. Quickly solder the negative lead to the metal shield of L28.

Time required for this modification is 15 minutes or less.
 

Symptom:
A close-in transmit spur might be present on early model TS-950(S) (serial number 1010xx and below) transceivers when operating at a dial frequency of approximately 14.200 MHz. This spur is seen approximately -40 to -50 dB down from the fundamental.

Cause:
The output from the mixer (IC12) which generates the final PLL loop comparison frequency for the AF unit contains harmonic radiation at approximately 36 to 68 MHz.

Parts required:

Qty   Description                          Kenwood Part No.  Circuit description
 1    Broad band transformer               L19-0346-05       L15
 1    .001 µF 50 V capacitor               CK45B1H103K       C127

Procedure:

1. Solder the primary of the transformer to pins 3 and 13 of IC12. You will have to bend the terminals slightly.
   
    
2. Solder the secondary of the transformer to pin 1 and 14 of IC12.
   
    
3. Remove chip capacitor C127 from the foil side of the board.
   
    
4. Connect pin 14 of IC12 to the ground pattern.
   
    
5. Add the new C127 from pin 1 of IC12 to L10 as shown in the accompanying illustration.

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.
 

Symptom:
After transmitting for approximately 2 hours at 50% duty with 150 watts output the temperature protection circuit activates reducing the output power to about 50 watts. Normally, full output power will be restored after the fans have had a chance to cool things down. Occasionally the power output will not return to normal, even after extended receive operations.

Cause:
The temperature sensor is attached to the main transformer and is set to activate at 80°C. This setting was selected to reduce power before the internal fuse on the transformer opens.

Correct action:
After through testing, we have found that the temperature sensor should be set to 90°C to allow proper return to full power transmit. This setting will also allow the radio to be used at higher ambient room temperatures without worrying about the power output dropping in the middle of a QSO.

Parts required:

Qty   Description                      Kenwood Part No.  Circuit description
 1    90°C Thermal switch                  S59-1416-05       S1

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.
 

Symptom:
During "Full Break-in" operation the SWR meter shows infinite SWR at the beginning of transmission. This results in a reduction of the transmitter power, followed by a gradual increase to normal full power. This symptom does not occur with the antenna tuner set to "THRU".

Cause:
Normally the RCB line should be 0 Vdc at the beginning of transmit operations. We have found that this does not always occur. The length of time required for transmit power to return to normally is directly related to the time constant of capacitor C128 on the RXB line.

Correct action:
Removing this capacitor corrects the above symptom, but might affect the receiver sensitivity at a dial frequency of 100 KHz. This action is only recommended if the symptom is actually present. Do not modify the unit if the symptom is absent.

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.
 

Symptom:
When tuning into an antenna with high SWR the SWR meter reading becomes unstable and a small amount of smoke is seen coming from the antenna tuner.

Cause:
One of the 3 x 4 self tapping screws that is used to secure the AT unit hinge can occasionally damage the insulation on the brown lead wire. When the tuner is then load into a high SWR the high reflected voltage causes the lead to head up, which further damages the insulation. Eventually the insulation breaks down completely and the wire shorts to the screw causing the lead to overheat and smoke to emanate from the area.

Correct action:
Cut a 12 cm long piece of the fiberglass insulating sleeve and install it over the brown lead wire to prevent shorting.

Parts required:

Qty   Description                          Kenwood Part No.  Circuit description
12 cm Fiberglass insulating sleeve         212-3502-05       W101

(Note: The insulating sleeve must be ordered in increments of 1 meter or greater).

Time required for this modification is 30 minutes or less.
 

Symptom:
A transmitter spur might be present at a dial frequency of xx.xx1 MHz. This spur (fo +/- 1 KHz) is quite small (-55 dB relative to fo) but might become noticeable when the transceiver is used with a linear amplifier.

Cause:
The transmitted signal enters pin 5 of IC11 which is in the last PLL loop in the AF unit due to RF feedback. This pin is the input for the 10 MHz Ref. Osc. signal from the CAR unit. IC11 is the source of the spurious signal since both the band and 10 MHz frequencies are divided by the 500 KHz comparison frequency supplies by IC11.

Correct action: To reduce this RF feedback increase the Ref. Osc. level from .2 V to .7 V ms by adding the accompanying circuit to the input of IC11.

Parts required:

Qty   Description                          Kenwood Part No.  Circuit description
 1    12 µH Ferri-inductor                 L40-1201-17       NA
 1    10 pF Chip capacitor                 CC73FCH1H100J     NA
 1    16 pF Chip capacitor                 CC73FCH1H160J     NA

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.
 

Symptom:
A click noise might be generated when receiving a strong signal (S-0 or above) when the NOTCH is ON and the Notch Control is turned away from the notch point.

Corrective action:
Lengthening the AGC release time of the IF Amp just before the NOTCH circuits will correct this symptom. The enclosed modification has been designed to change the time constant only when the NOTCH circuit is activated. Do not install this modification on sets that do not exhibit this symptom as the AGC FAST time constant affected by this change.

1. Cut the printed circuit foil pattern between the test point (TP) and gate 2 of Q2 as shown.
   
    
2. Install the 47 Kohm chip resistor from TP tp gate 2 of Q2.
   
    
3. Add a 0.047 µF ceramic capacitor as shown in the accompanying illustration.
   
    
4. Add the DTC124ES transistor as show.
   
   Note: The .047 µF capacitor and the digital transistor must be connected together as shown and installed so that they do not touch the sorrounding board patterns.
   
    
5. Install a jumper wire from the base of the digital transistor to pin number 6 of CN14.

Parts required:

Qty   Description                          Kenwood Part No.  Circuit description
 1    0.047 µF capacitor                   CK45B1H473Z       NA
 1    Digital transistor                   DTC124ES          NA
 1    47 Kohm chip resistor                RK73FB2A473J      NA

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.
 

Symptom:
When the YG-455S-1 is installed, the LSB audio is slightly off pitch. This characteristic is corrected using the "Service Adjustment" menu. Early models of this transceiver did not make this adjustment available the individual operator unless they had access to a service manual.

Countermeasures:
A menu option has been added to Menu 07 on late versions of the transceiver which allows the individual operator to "correct" this audio shift. This has been accomplished by changing the program of the ROM chip IC-19 on the Digital unit X46-3130 1/2, and by updating the operators manuals. Installing the new ROM on early versions of this transceiver will allow the operator the same convenience as provided on later serial numbered sets.

Parts required:

Qty   Description           Old part No.      New Part No    Circuit Description
 1    ROM                   27C512BJDUF       27C512BJDUG    IC-19
                                or
 1    ROM                   27C512RJDVF       27C512BJDUG    IC-19
 1    Instruction manual    B62-0229-30       B62-0229-40

Time required for this modification is 30 minutes or less 

Symptom:
Using the following key sequence will result in a failure to receive on VFO B.

1. Select different frequencies for VFO A and B. (Example: 14.019 for VFO A and 14.018 for VFO B. Mode SSB, 2.7 KHz FILTER for 455 KHz and 8.83 MHz).
   
    
2. Select VFO A to RX and VFO B to TX. The press the TF-W key.
   
    
3. Press the ENT key and select a frequency in the 7 MHz band. (For example: 7.018 MHz for VFO A and 7.019 for VFO B).
   
    
4. Press the ENT key and reselect the 14 MHz band.
   
    
5. Change VFO B from TX to RX. The FILTER display for 8.83 dissapears and reception is disabled on VFO B.'

Countermeasure:
Press the 8.83 MHz FILTER select key one time, or replace the ROM chip.

Parts required:

Qty   Description              Old part No.   New Part No    Circuit Description
 1    ROM                      27C512BJDUG    27C512BJDUJ    IC-19
                                   or
 1    ROM                      27C512BJDVG    27C512RJDVJ    IC-19

Time required for this modification is 30 minutes or less.
 

Symptom:
The background audio tone is different between the LSB and the USB mode, when no signal is present, i.e. the carrier point is incorrect. Occasionally, this tone is still different after adjustment per the service manual, specifically Item 9 on page 196.

Countermeasure:
Change the adjustment procedure for Item 9 as follows:

Test Equipment

• Two RF signal generators with good frequency accuracy.
• A two-signal combiner.
• An oscilloscope.

Preparation:

1. Adjust the two signal generators for equal output levels.
   
    
2. Connect the test equipment as shown in the accompanying diagram.
   
    
3. Set the frequency of SSG1 to 1.850.2 MHz.
   
    
4. Set the frequency of SSG2 to 1.852.8 MHz.
   
    
5. Fine tune the output levels of the two SSG's for a good two-tone output on the oscilloscope (Figure 3).

Adjustment Procedure:

1. Connect the transceiver and the test equipment as shown in figure 2.
   
    
2. Select the adjustment Mode on the transceiver by pressing and holding the 3 and 9 keys on the keypad while the POWER is turned on.
   
    
3.  
   • Set the output of the two signal generators for a - 73 dBm level.
   • Set the SSB SLOPE TUNE control to the NORMAL position.
   • Set the AGC to AUTO
   • Select MENU 00 using the M.CH/VFO knob.
   • Select USB mode.
   • Press the 8.83 MHz filter key until there is no indicator illuminated (no filter).
   • Press the 455 KHz filter key until 2.7 K appears in the display.
   • Set the frequency to the transceiver to 1.850.0 MHz.
   • Adjust the TX VFO/SUB encoder control until the waveforms displayed on the oscilloscope cross as shown in figure 3.

   
   
    

4.  
   • Switch to LSBV.
   • Press the 8.83 MHz filer key until 6 KHz appears in the display.
   • Leave the 455 KHz filter set at 2.7 KHz.
   • Select a dial frequency of 1.853.0 MHz.
   • Adjust the TX VFO/SUB encoder control until the waveforms displayed on the oscilloscope cross as shown in figure 3.

   
   
    

5.  
   • Select MENU 01.
   • Switch to USB.
   • Press the 8.83 MHz filter key until 2.7 KHz appears in the display.
   • Leave the 455 KHz filter set at 2.7 KHz.
   • Select a dial frequency of 1.850.0 MHz.
   • Adjust the TX VFO/SUB encoder control until the waveforms displayed on the oscilloscope cross as shown in figure 3.

   
   
    

6.  
   • Select LSB.
   • Select a dial frequency of 1.853.0 MHz.